Head Gasket Complication

The primary cause of rod knock is running the engine low on oil. High engine RPMs and normal wear and tear can contribute as well. If the engine ran low on oil before the leak was fixed, there is a chance that the damage that leads to a rod knock may have already started developing. When we take the engine out to reseal the camshaft carriers, we drain all of the oil out of it. This necessary process can accelerate the connecting rod bearings failing if the process was already started. No part of the standard camshaft carrier reseal will cause this failure.

Unfortunately, there is no way to tell if the engine has the beginning of a rod knock failure before the sound presents. The only way to visually inspect for this would be to completely disassemble the short block, which would add several thousand dollars to the repair. Without symptoms present, there is no justification to perform that procedure, with its high cost, as preventative.

If the engine ran low on oil, the odds of this failure go up significantly.

We see about one out of fifty engines develop a rod knock within 10,000 miles of a camshaft carrier reseal. Sometimes it can happen right after service, sometimes it can take several thousand miles. If the engine has run low on oil, the odds of this failure go up significantly.

The fix for this failure is to replace or rebuild the short block. The short block is the portion of the engine that houses the crankshaft and pistons. This can be very expensive, as well as very time-consuming to access. The exact price and timeframe will vary by engine and replacement part availability.

If the short block does fail within the warranty period on the camshaft carriers, we will help with the cost. There are two elements to the short block replacement; the short block itself and the labor and parts kit to replace it. You will be responsible for the full cost of the replacement short block, but the parts kit and labor needed to install the short block will be covered on a prorated scale based on mileage since the original camshaft carrier reseal. If your short block fails within the first 1,000 miles of the warranty, we will cover 100% of the parts kit and labor. After the first 1,000 miles, the amount we discount will be equal to the percentage of the 12,000-mile warranty that remains. Once the warranty has expired, by mileage or time, there will be no discount toward a short block replacement.

The primary cause of warped short block decks is severe engine overheating. We do see this happen from time to time without a severe overheating condition. It is also possible that a previously done head gasket repair where the prior shop did not properly clean these deck surfaces can cause the surface variation to be in the decks. If the engine did not overheat, the odds of this failure are very low.

We see about one out of fifty engines with short block deck surfaces that are warped beyond specification. If the engine severely overheated, the odds of this failure go up significantly.

We have two options:

1. Apply a spray-on coating to the head gasket that may assist in sealing the head gasket. This fix doesn’t add any additional cost to the repair. This is only an option if the deck surfaces are out of spec by a small amount. This method will void the warranty on the head gaskets, as this is not considered to be a “proper” repair. We cannot guarantee this will solve the leak.
2. Disassemble the short block so the short block deck surfaces can be resurfaced by a machine shop. This will add a significant cost to the repair but will maintain the warranty. This is effectively a rebuild or reconditions of the short block.

The most common cause of oil consumption is having run an engine with a low oil level. The lack of lubrication will cause scoring on the cylinder walls, which will result in some of the oil sneaking past the piston rings. But even if the engine never ran low on oil, normal wear and tear can cause this. Sometimes, major engine repairs can accelerate the rate of consumption.

Most Subarus with more than 100k miles will experience some form of oil consumption. Severe oil consumption, or more than a quart every 1,000 miles, is rare. We see about one out of fifty engines with severe oil consumption. If the engine ran low on oil, the odds of this failure go up significantly.

The easiest and most economical way to address this issue is to check and top off the engine oil on a regular basis. We understand that this is not always convenient. There are also oil additives that can help slow the process.

The full solution to this issue is to rebuild the short block. This option will cost thousands of dollars. Drivers very rarely choose to go this route due to the high cost.

The rotating camshaft is held away from the housing it sits in by a very thin layer of pressurized oil. If there is debris in the oil, or if the oil pressure drops from a lack of oil in the engine, these smooth, precision-machined surfaces will start to rub on each other. This will make them rough and they will start to bind up to each other. They will eventually seize up, causing catastrophic engine failure.

This is not a very common failure. We see this happen on about one out of seventy-five engines. If the engine ran low on oil, the odds of this failure go up significantly.

If the damage is minor, we may be able to polish the bearing surfaces smoothly again. If the damage is severe, we will need to replace the damaged cylinder head. The cost for that will vary depending on part availability.

There are a variety of things that can fall under this type of failure. One of the best examples is a timing belt tensioner that won’t hold tension. If we were to reinstall a failing tensioner, the resulting repairs could cost thousands of dollars. These failures are rarely the fault of the driver. Typically, these things are parts that are well past their useful life.

We see crucially failing parts on about one out of twenty-five engines.

The exact fix will depend on what is failing. We will always do our best to get your permission before proceeding with repairs that exceed what you have already authorized. However, if it is not possible for us to continue without a certain repair, and we have been unable to reach you by phone, text, and email for more than 3 hours, we may authorize up to $300 in additional repairs on your behalf.

Catalytic converters wear out over time. The high-temperature chemical reactions that take place in the cat will slowly become less efficient. Driving your car with an active misfire, out-of-specification fuel trims, or while internally burning oil may accelerate the failure. A faulty cat test sensor may cause the test to fail.

When we remove the engine from the car to perform the camshaft carrier reseal, we disconnect the battery. This resets the engine computer. When the computer is powered back up, it has to rerun all of its tests on the cat. If a cat was close to failure before, it may fail this retest. It may take a few days to a few weeks of regular driving for the vehicle to retest the cat.

Catalytic converter failure is pretty common on Subaru’s over 100k miles. The vehicles made from 2000 through 2015 seem to be more susceptible. About one in fifteen will see a cat test failure after resealing the camshaft carriers. Most will see this failure before 200k miles.

If the cat fails, the correct fix is to replace the cat. If the sensor fails, then replace the sensor. There are fuel system additives that claim to clean up the cat, but we haven’t seen any convincing evidence that these additives work well. Cats can cost anywhere from a few hundred dollars to two thousand, as they contain rare metals. The sensor costs a few hundred dollars to replace.

The radiator is a big tank that’s made out of aluminum and plastic with many very small passages. The plastic is designed to operate within a certain temperature range. If you experienced overheating before your service, there’s a good chance that the plastic and seals in the radiator were compromised and weakened by exceeding this temperature range. This can cause problems during or after the repair as the plastic is now brittle.

If engine issues caused oil to mix into the coolant, there’s also a good chance that the foreign oil caused chemical damage to the plastic in the radiator and the seals where the plastic and aluminum meet. It is significantly more common for radiators to fail after oil has mixed into the coolant. This damage isn’t visible and will first become apparent when a leak forms. These leaks may not appear until after the engine repairs are complete.

These concerns are mostly related to overheating or oil contaminated coolant. About one out of four cars with these symptoms will have a radiator failure in the short term and more in the long term. It is possible for radiators to have leaks without these issues as radiator leaks are somewhat common without related symptoms. About one in twenty vehicles will have radiator issues after service, even without these symptoms being present.

The solution for a failed radiator is to replace it. If you did have overheating or contaminated coolant issues, we may recommend replacing the radiator proactively during the engine repair. We will always inspect the radiator closely during service for warning signs of pending failure. It’s several hundred dollars cheaper to replace the radiator when it’s already out of the car for the engine repairs. We can also avoid the tow bill that’s usually needed if the radiator fails away from the shop.